Spring Mechanisms for Clocks
A spring-loaded arm on an irregular cam wheel, and how its thrust shifts from perpendicular to oblique
This folio studies two spring devices for clocks, in each of which a spring presses a pivoting arm against an irregular (cam) wheel. Analyzing the second, with the arm pivoting at m and meeting the wheel at b whose center is n, the note traces how the direction of the arm's thrust changes as the wheel turns from b toward a. At first the push is at right angles toward the center along b to n; toward the end it becomes oblique, running beyond the center along a to b, before the passage breaks off.
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Two spring devices bearing on an irregular cam
Two spring mechanisms for clocks are shown, each pressing a pivoting arm against an irregular cam wheel. In the second, the arm pivots at m and meets the wheel at b, whose center is n; an analytical line from m to n cuts the wheel at a.
Thrust shifting from perpendicular to oblique
As the irregular wheel turns from b toward a, the arm at first pushes at right angles toward the center, along b to n. Toward the end of the motion it pushes at an oblique angle beyond the center, along the line a to b. The note then breaks off.